Benzofuranone or indolinone compounds useful as stabilizers for organic materials

ABSTRACT

The present invention relates to a process for stabilizing organic polymeric materials comprising incorporating therein a benzofuran (2) one or indolin (2) one compound as stabilizer. Such stabilized polymeric materials are stabilized against degradation during the polymer processing.

The present invention relates to a process for stabilizing organic polymeric materials employing benzofuranone or indolinone compounds as stabiliser.

Accordingly, the present invention provides a process for stabilising organic polymeric materials comprising incorporating therein a compound of formula I_(c), ##STR1## in which either

R is hydrogen,

and R₁ is hydrogen; C₁₋₂₂ alkyl; C₅₋₆ cycloalkyl; C₁₋₅ alkyl-C₅₋₆ cycloalkyl; phenyl; phenyl substituted by a total of up to three substituents selected from the group consisting of C₁₋₁₂ alkyl (up to three of these with max. 18 carbon atoms in the combined alkyl substituents), hydroxyl (max. of two of these), C₁₋₁₂ alkoxy, C₁₋₁₈ acyloxy, chlorine and nitro (max. of one of each of these); a group of formula (a/4), (a/5) or (a/6) ##STR2## or R and R₁ together form a group (a/2) ##STR3## X is --O-- or ##STR4## with the proviso that when X is ##STR5## R₁ is other than (a/5), either,

each of R₂, R₃, R₄ and R₅, independently, is hydrogen; C₁₋₁₂ alkyl;

max. two of R₂ to R₅ are:

C₅₋₆ cycloalkyl; C₁₋₅ alkyl-C₅₋₆ cycloalkyl; hydroxyl; C₁₋₂₂ alkoxy; phenoxy optionally substituted by up to two C₁₋₁₂ alkyl groups with a total of up to 16 carbon atoms in the combined alkyl substituents; C₁₋₁₈ -acyloxy; phenylcarbonyloxy; chlorine; max. one of R₂ to R₅ is:

phenyl-C₁₋₉ alkyl or phenylthio in which the phenyl nucleus is optionally substituted by up to three substituents selected from C₁₋₁₂ alkyl, hydroxyl, and R₁₅ CO--O--; phenyl optionally substituted by up to two C₁₋₁₂ alkyl groups with a total of up to 16 carbon atoms in the combined substituents; nitro; 2-furanyl- or 2-thienylcarbonyloxy; ##STR6##

(a/4); or (a/5) as R₃ or R₅, with the proviso that when R and R₁ are hydrogen R₂ to R₅ are other than hydroxyl, and when R₁₁ in (b/2) is other than hydrogen such (b/2) group is adjacent to a hydroxyl group,

or R₂ and R₃, together form a condensed benzene ring,

or R₃ and R₄, together, when X is --O--, form a furan(2)one ring in which the 3-position bears the groups R and R₁ as defined above,

or R₄ and R₅, together form tetramethylene or when X is --O-- form a furan(2)one ring in which the 3-position bears the groups R and R₁ as defined above,

and one of the two remaining substituents R₂, R₃, R₄ and R₅ is hydrogen and the other is any one of the significances given for R₂ to R₅, above,

either R₆ is C₁₋₁₈ alkyl; C₅₋₆ cycloalkyl; C₁₋₅ alkyl-C₅₋₆ cycloalkyl; benzyl; (C₆ H₅)₂ CH; phenyl optionally substituted by one or two C₁₋₁₂ alkyl groups (total no. of carbon atoms in combined substituents is max. 16), one hydroxy, one or two methoxy groups, one chlorine or one dimethylamino; 3,5-di-tert.-butyl-4-hydroxyphenyl; β-naphthyl; pyridinyl; 2-furyl; ##STR7##

and R_(6a) is hydrogen, C₁₋₁₈ alkyl (C₅₋₆)cycloalkyl, C₁₋₅ alkyl-C₅₋₆ cycloalkyl, phenyl or benzyl,

or, R₆ and R_(6a) together with the C-atom to which they are bound form a 5- or 6-membered aliphatic ring which is optionally substituted by a C₁₋₄ alkyl group,

each R₇, independently, is hydrogen; C₁₋₁₈ alkyl; alkyl-O-alkylene with a total no. of up to 18 carbon atoms; alkyl-S-alkylene with a total no. of up to 18 carbon atoms; di-C₁₋₄ -alkylaminoC₁₋₈ alkyl; C₅₋₇ cycloalkyl; or phenyl optionally substituted by up to 3 C₁₋₁₂ alkyl groups with a total no. of up to 18 carbon atoms in the combined substituents;

either, each R₈, independently, is hydrogen; C₁₋₁₈ alkyl; C₅₋₆ cycloalkyl; C₁₋₅ alkyl-C₅₋₆ cycloalkyl; phenyl optionally substituted by up to two C₁₋₁₂ alkyl groups with max. 16 carbon atoms in the combined substituents; ##STR8##

or, both R₈ together with the nitrogen form piperidine or morpholine,

R₉ has one of the significances of R₈,

R_(9a) is hydrogen, C₁₋₁₈ alkyl, (d/1), (d/2) or (d/3),

R_(10a) is hydrogen, C₁₋₁₈ alkyl, C₅₋₆ cycloalkyl, C₁₋₅ alkyl C₅₋₆ cycloalkyl, phenyl optionally substituted by up to two C₁₋₁₂ -alkyl groups with max. 16 carbon atoms in the combined substituents or benzyl,

R₁₁ is hydrogen, C₁₋₂₂ alkyl, C₅₋₇ cycloalkyl, phenylC₁₋₆ alkyl or phenyl optionally substituted by up to two C₁₋₁₂ alkyl groups with max. 16 carbon atoms in the combined substituents.

R₁₂ is C₁₋₁₈ alkyl, 2-hydroxyethyl, phenyl or (C₁₋₉)alkylphenyl,

R₁₅ is C₁₋₂₂ alkyl or phenyl, and

n is 0, 1 or 2.

When X is NR_(10a) and R_(10a) is phenyl then R₁ is preferably an optionally substituted phenyl.

R is preferably hydrogen.

R₁ is preferably R₁ ', where R₁ ' is hydrogen; C₁₋₁₈ alkyl; phenyl optionally substituted by one or two C₁₋₈ alkyl groups and/or a hydroxyl group; (a/4) or (a/5) or together with R is (a/2). More preferably R₁ is R₁ ", where R₁ " is C₁₋₁₈ alkyl, or phenyl optionally substituted by one or two C₁₋₈ alkyl groups and/or a hydroxyl group. Most preferably R₁ is phenyl optionally substituted by C₁₋₄ alkyl, with unsubstituted phenyl being especially preferred.

When R₁ is optionally substituted phenyl, such phenyl preferably bears no chlorine atom. When R₁ as substituted phenyl bears a hydroxyl group said hydroxyl group is preferably adjacent to a branched alkyl group such as tert.-butyl, more preferably located between two such groups.

When R₁ is phenyl substituted by an acyloxy group preferably such group is in the 2- or 4-position and preferably a C₁₋₄ alkyl group is also present especially in para position to the acyloxy group.

When R₁ is optionally substituted phenyl, R₂ is preferably hydrogen or methyl, more preferably hydrogen.

When any two of R₂ to R₅ form a condensed benzene ring, tetramethylene or a condensed furan(2)one ring as defined above preferably both the other substituents are hydrogen or one is hydrogen and the other is C₁₋₄ alkyl or COOH, most preferably both are hydrogen. When X is ##STR9## the R₃ to R₅ are preferably other than tert. alkyl groups.

When anyone of R₂ to R₅ is phenylalkyl or phenylthio in which the phenyl nucleus is substituted as defined above, preferably said phenylalkyl or phenylthio group is R₃ or R₅, more preferably R₅.

Furthermore, when such substituent is present as R₃ preferably R₂ and R₄ are hydrogen and R₅ is hydrogen or alkyl (pref. C₁₋₅) and when such a substituent is present as R₅, preferably R₂ and R₄ are hydrogen and R₃ is hydrogen or alkyl (pref. C₁₋₈ especially tert. octyl). Preferred phenylalkyl or phenylthio groups in the case of R₅ are those in which the phenyl nucleus has a hydroxy or R₁₅ CO--O--substituent in ortho position to the alkyl or thio group. Preferred such groups are: ##STR10## in which

each R_(x), independently, is hydrogen or (C₁₋₄)-alkyl,

R_(y) is hydrogen or CO-R₁₅, and

each R_(z), independently, is hydrogen, C₁₋₉ -alkyl (linear or branched) and

R_(z) ' is hydrogen or C₁₋₄ linear alkyl.

In the group (PA) preferably each R_(x), independently, is hydrogen or C₁₋₄ alkyl, more preferably hydrogen or methyl; each R_(z) independently, is preferably hydrogen or C₁₋₄ alkyl more preferably hydrogen, methyl or tert. butyl with hydrogen or methyl being most preferred. R_(z) ' is preferably hydrogen or methyl, most preferably hydrogen. In the group (PT) each R_(z), independently, is preferably hydrogen or (C₁₋₈)alkyl, more preferably, the R_(z) ortho to OR_(y) is hydrogen and the other tert. octyl. R_(z) ' is preferably hydrogen.

R₂ is preferably R₂ ', wherein R₂ ' is hydrogen, (C₁₋₄)alkyl or together with R₃ ' forms a condensed benzene ring. More preferably R₂ is R₂ ", where R₂ 41 is hydrogen or methyl, especially hydrogen.

R₃ is preferably R₃ ', where R₃ ' is hydrogen, C₁₋₁₂ alkyl, phenyl, C₁₋₁₈ alkoxy, phenoxy, C₁₋₁₈ alkylcarbonyloxy, (a/4), (a/5), (b/2), (b/4) or together with R₂ ' forms a condensed benzene ring or together with R₄ ' forms a furan(2)one nucleus in which R is hydrogen and R₁ is preferably R₁ ". More preferably R₃ is R₃ ", where R₃ " is hydrogen, (C₁₋₁₂)alkyl, phenyl, (a/4) or together with R₂ ' forms a condensed benzene ring. Even more preferably R₃ is R₃ "', where R₃ "' is hydrogen, (C₁₋₉)alkyl or (a/4). Most preferably R₃ is R₃ "", where R₃ "" is hydrogen or alkyl C₁₋₉ (preferably C₁₋₅), with methyl, tert.-butyl or tert.-amyl being most preferred.

When R₃ ' forms a furanone ring together with R₄ ' the oxygen atom of said nucleus is preferably bound to the R₄ ' position. When R₃ is (b/2) and R₁₁ is other than hydrogen the adjacent hydroxyl group is preferably in the 6-position.

R₄ is preferably R₄ ', where R₄ ' is hydrogen, C₁₋₁₂ alkyl, C₁₋₁₈ alkoxy, phenoxy or together with R₃ ' or R₅ ' forms a furan(2)one ring in which R is hydrogen and R₁ is preferably R₁ " or R₄ ' together with R₅ ' forms tetramethylene. More preferably R₄ is R₄ ", where R₄ " is hydrogen C₁₋₁₂ alkyl, C₁₋₁₈ alkoxy or phenoxy. Even more preferably R₄ is R₄ "', where R₄ "' is hydrogen or C₁₋₁₂ alkyl, especially hydrogen. The preferred alkyl groups as R₄ are C₁₋₈ alkyl, more preferably C₁₋₄, with methyl and tert.-butyl being the most preferred alkyl groups.

When R₄ ' together with R₅ ' forms a furan(2)one nucleus the oxygen atom of said nucleus is preferably bound to the 7-position.

R₅ is preferably R₅ ', where R₅ ' is hydrogen, C₁₋₁₂ alkyl, phenyl, (a/4), (a/5), (PA), (PT) or together with R₄ ' forms tetramethylene or a furan(2)one ring. More preferably R₅ is R₅ ", where R₅ " is hydrogen, C₁₋₁₂ alkyl, (PA) or (PT). More preferably R₅ is R₅ "', where R₅ "' is hydrogen or C₁₋₈ alkyl with alkyl, preferably C₁₋₅ alkyl, being most preferred. The preferred C₁₋₅ alkyl groups are methyl, tert.-butyl and tert.-amyl.

When a furan(2)one nucleus is formed by any two of R₃ ' to R₅ ' preferably the R₁ 's are the same. Most preferably they are phenyl.

X is preferably X', where X' is --O-- or --NR_(10a) '-- in which R_(10a) ' is hydrogen, C₁₋₁₂ alkyl, preferably C₁₋₄ alkyl, or phenyl. More preferably X is --O--, --N(C₁₋₄ alkyl)-- or --N(C₆ H₅)--. Most preferably X is O.

When R₆ is substituted phenyl, such phenyl is preferably hydroxyphenyl, phenyl substituted by up to two C₁₋₁₂ alkyl groups with max. 16 carbon atoms in the combined substituents or 3,5-di-tert.-butyl-4-hydroxyphenyl; more preferably any substituted phenyl as R₆ is mono substituted by one C₁₋₁₂ -alkyl group or is 3,5-di-tert.-butyl-4-hydroxyphenyl. Preferably any phenyl as R₆ is unsubstituted. Any alkyl as R₆, preferably contains 1 to 12, more preferably 1 to 8, most preferably 1 to 4 carbon atoms.

R₆ is preferably R₆ ', where R₆ ' is C₁₋₁₈ alkyl, phenyl, 3,5-di-tert.-butyl-4-hydroxyphenyl, (c/1) or together with R_(6a) is cyclohexylidene. More preferably R₆ is R₆ ", where R₆ " is C₁₋₁₂ alkyl, phenyl, 3,5-di-tert.-butyl-4-hydroxyphenyl or together with R_(6a) and the common C-atom form cyclohexylidene. Most preferably R₆ is R₆ "', where R₆ "' is C₁₋₁₂ alkyl or phenyl.

Any alkyl as R_(6a) preferably contains 1 to 12, more preferably 1 to 8, most preferably 1 to 4 carbon atoms, especially methyl.

R_(6a) is preferably R_(6a) ', where R_(6a) ' is hydrogen, C₁₋₁₂ -alkyl or together with R₆ and the common C-atom forms cyclohexylidene. Most preferably R_(6a) is hydrogen. When R₆ is substituted phenyl or CH(C₆ H₅)₂ or (c/1) R_(6a) is preferably hydrogen.

R₇ is preferably R₇ ', where R₇ ' is hydrogen, C₁₋₁₈ alkyl, phenyl optionally substituted by up to two C₁₋₁₂ alkyl groups with max. 16 carbon atoms in the combined substituents. More preferably R₇ is R₇ ", where R₇ " is C₁₋₁₈ alkyl, phenyl or C₁₋₁₂ alkylphenyl. Most preferably R₇ is C₁₋₁₈ alkyl, especially C₈₋₁₈ alkyl.

Each R₈, independently, is preferably R₈ ', where R₈ ' is hydrogen, C₁₋₁₈ alkyl or both R₈ ' together with the N-atom form piperidine. More preferably each R₈, independently is hydrogen or C₁₋₁₈ alkyl. Preferred alkyl groups as R₈ are C₁₋₁₂ --, preferably C₁₋₈ --, most preferably C₁₋₄ alkyl.

R₉ is preferably R₉ ', where R₉ ' is hydrogen, C₁₋₈ alkyl or (d/1). More preferably R₉ is hydrogen or C₁₋₈ alkyl. Any alkyl as R₉ preferably contains 1 to 8, more preferably 1 to 4 carbon atoms.

R_(9a) is preferably R_(9a) ', where R_(9a) ' is hydrogen, C₁₋₈ --alkyl or (d/1). Any alkyl as R_(9a) preferably contains 1 to 8, more preferably 1 to 4 carbon atoms.

R₁₁ is preferably R₁₁ ', where R₁₁ ' is hydrogen, C₁₋₁₈ alkyl or phenyl. R₁₁ in (b/2) is preferably phenyl.

Any alkyl as R₁₁ preferably contain 4 to 17 carbon atoms.

R₁₂ is preferably R₁₂ ', where R₁₂ ' is C₁₋₁₂ alkyl, phenyl or 4-(alkyl C₁₋₉)phenyl.

n in (a/4) or (a/5) as R₁ is preferably 1.

n in (a/4) or (a/5) as R₅ is preferably 1.

n in (a/4) or (a/5) as R₃ is preferably 2.

The preferred cycloalkyl groups are cyclohexyl and methylcyclohexyl, especially cyclohexyl.

Preferred compounds of formula I_(c) are those in which R₁ is R₁ ',R₂ is R₂ ', R₃ is R₃ ', R₄ is R₄ ',R₅ is R₅ ' and X is --O--. More preferred compounds are those where R is hydrogen, R₁ is R₁ ", R₂ is R₂ ", especially hydrogen, R₃ is R₃ ", preferably R₃ "', R₄ is R₄ " and R₅ is R₅ ". Especially preferred are those compounds where R is hydrogen, R₁ is C₁₋₄ alkylsubstituted phenyl, or phenyl, especially phenyl, R₂ is hydrogen, R₃ is R₃ "", R₄ is hydrogen and R₅ is R₅ "' especially C₁₋₅ alkyl.

The compounds of formula I_(c) are either known or may be prepared from available starting materials in accordance with known methods.

The benzofuran (2) one compounds in which both R and R₁ are hydrogen are preferably prepared by reacting a compound of formula III ##STR11## in which

R₂ to R₅ are as defined above with the exception that they are other than (a/5) and that in any group (a/4) or (b/4) present R₇ is hydrogen, and

G is a secondary amine group of halogen, with an ionic cyanide compound, hydrolising the product thereof, followed by ring closure condensation.

This process forms part of the present invention. G is preferably--N(C₁₋₄)alkyl₂, especially--N(CH₃)₂, or morpholine or piperidine. Any halogen as G is preferably chlorine or bromine, especially chlorine. Suitable ionic cyanide compounds are alkali- or alkaline earth cyanides, more preferably sodium- or potassiumcyanide. Each of the reaction steps may be carried out in accordance with known methods for such type of reactions.

It will be appreciated that the end product can be esterified in order to obtain products where R₇ is other than hydrogen.

The compounds of formula III are either known or may be prepared in accordance with known methods from available starting materials.

The compounds of formula I_(c) may be incorporated into the polymeric material to be stabilized before, during, or after polymerization.

The amount of compound of formula I_(c) incorporated may vary according to the material to be stabilized and the ultimate use to which it is to be put. Suitable amounts are from 0.01 to 5% preferably from 0.05 to 1%, based on the weight of the materials to be stabilized. The organic polymeric materials to be stabilized may be natural or synthetic polymeric materials. Examples of such materials include rubber, polyolefins, especially polyethylene, polypropylene, ethylene, propylene copolymers, polybutylene, polystyrene, chlorinated polyethylene, PVC, polyester, polycarbonate, polymethylmethacrylate, polyphenyleneoxide, polyamides such as nylon, polyurethanes, polypropyleneoxide, phenol-formaldehyde resins, epoxy resins, polyacrylonitrile and corresponding copolymers such as acrylonitrile butadiene styrene (ABS) terpolymers.

The process of the present invention is preferably employed to stabilise polypropylene, polyethylene, ethylene/propylene copolymers, PVC, polyesters, polyamides, polyurethanes, polyacrylonitrile, ABS terpolymers, terpolymers of acrylic ester, styrene and acrylonitrile, copolymers of styrene and acrylonitrile and styrene/butadiene copolymers. The most preferred organic polymeric materials are polypropylene, polyethylene especially HDPE, ethylene/propylene copolymers and ABS.

The incorporation of the compounds of formula I_(c) in the material to be stabilized is effected in accordance with known methods. Preferred methods are those in which the compounds of formula I_(c) are incorporated in the polymeric material by melt blending the stabiliser and the additives in conventional equipments such as Banbury mixers, extruders etc. Polypropylene and polyethylene granulates on powders are advantageously employed, whereby the compounds of formula I_(c) are admixed with said powders and then extruded etc and worked into the films, foils, bands threads etc.

The process of the present invention may be carried out by incorporating a compound of formula I_(c) alone or together with other additives e.g. further stabilisers etc.

The preferred process according to the present invention comprises incorporating a compound of formula I_(c) and either

(i) a stabiliser of the sterically hindered phenol type,

or (ii) a sulphur-containing or phosphorous containing stabiliser,

or (i) and (ii), into the polymeric material.

The ratio of stabiliser (i) or (ii) to the compounds of formula I_(c) incorporated in the polymeric material is suitably 5:1 to 1:5, preferably 2:1 to 1:1. The ratio of combined (other) stabilisers to compounds of formula I_(c) is suitably 15:1 to 1.5, preferably 6:1 to 1:3. Preferably, when only stabilisers (i) are employed with the compounds of formula I_(c) the ratio of compounds (i) to those of formula I_(c) is 3:1 to 1:1.

Examples of sterically hindered phenols are: - β-(4-hydroxy-3,5-ditert.-butylphenyl)-propionicacidstearylester, tetrakis[methylene-3(3',5'-ditert.-butyl-4-hydroxyphenyl)-propionate]-methane, 1,3,3-tris-(2-methyl-4-hydroxy-5-tert.-butylphenyl)-butane, 1,3,5-tris(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl)-1,3,5-triazine-2,4,6-(1H,3H,5H)-trione, bis(4-tert.-butyl-3-hydroxy-2,6-dimethylbenzyl)-dithiolterephthalate, tris(3,5-ditert.-butyl-4-hydroxybenzylisocyanurate, triester of 3,5-di-tert.-butyl-4-hydroxyhydrocinnamic acid with 1,3,5-tris(2-hydroxyethyl)-s-triazin-2,4,6-(1H,3H,5H)-trione,bis [3,3-bis-4'-hydroxy-3-tert.-butylphenyl)-butaneacid]-glycolester, 1,3,5-trimethyl-2,4,6-tris-(3,5-ditert.-butyl-4-hydroxybenzyl)-benzene, 2,2'-methylene bis (4-methyl-6-tert.-butylphenyl) terephthalate, 4,4-methylene-bis-(2,6-ditert.-butylphenol), 4,4'-butylidene-bis(6-tert.-butyl-meta-cresol), 4,4-thio-bis(2-tert.-butyl-5-methylphenol), 2,2'-methylene-bis(4-methyl-6-tert.-butylphenol.

Examples of sulphur containing stabilisers are distearylthiodipropionate, dilaurylthiodipropionate, tetrakis(methylene-3-hexylthiopropionate)-methane, tetrakis (methylene-3-dodecylthiopropionate)-methane and dioctadecyldisulphide.

Examples of phosphorous containing compounds are trinonylphenylphosphite, 4,9-distearyl-3,5,8,10-tetraoxadiphosphaspiroundecane,tris-(2,4-ditert.-butylphenyl)phosphite and tetrakis(2,4-ditert.butylphenyl)-4,4'-diphenylene diphosphonite.

In addition to the above further stabilisers, U.V. absorbers as described in DOS 2 606 358 e.g. 2-(2'-hydroxyphenyl)-benztriazole, 2-hydroxybenzophenone, 1,3-bis(2-hydroxybenzoyl)benzene, salicylates, cinnamic acid esters, hydroxybenzoic acid esters, sterically hindered amines and oxylic acid diamides. Suitable such compounds are described in DOS No. 2 606 358.

Metal deactivators for example N,N'-dibenzoylhydrazide, N-benzoyl-N'-salicyloylhydrazide, N,N'-distearylhydrazide, N,N'-bis-[3-(3,5-ditert.-butyl-4-hydroxyphenyl)-propionyl]hydrazide, N,N'-bis-salicyloylhydrazide, oxalylbis-(benzylidenehydrazide), N,N'-bis(3-methoxy-2-naphthoyl-)hydrazide, N,N'-di-α-phenoxy-butyloxy (isophthalyl-dihydrazide) may also be incorporated into the polymeric material.

Additional conventional additives may also be employed for example, flame retardants, antistatic agents etc.

Furthermore, an optical brightener may be incorporated in the polymer to be stabilised and so that the distribution of the additives which are intimately admixed with said optical brightener may be ascertained by fluorescence intensity measurements.

The present invention also provides master batches of polymeric organic materials containing 5 to 90%, perferably 20 to 60%, more preferably 20-30% of a compound of formula I_(c). Such master batches may then be admixed with unstabilised polymeric material. It is to be appreciated that such master batches may also contain additional additives such as those stated above.

Polymeric materials containing a compound of formula I_(c) are primarily stabilised against degradation during processing. When, of course, other additives such as antioxidants, e.g. above phenols, and U.V. absorbers are also employed together with the compounds of formula I_(c), the polymeric material has an enhanced long term stability against thermal- and photoxidative degradation.

The following examples further serve to illustrate the invention. In the examples all parts are by weight, and all temperatures are in degrees Centigrade.

EXAMPLE 1

15.2 Parts mandelic acid and 20.6 parts 2,4-di-tert.-butyl phenol are mixed together and heated under a nitrogen atmosphere to 185° for c. 20 hours. Water is distilled off. After cooling, the reaction mixture is dissolved in ether and extracted with an aqueous sodium bicarbonate solution and then with water. After evaporating-off the solvent and recrystallizing from methanol a compound having a melting point of 113°-114° and of the formula of the 4th compound in Table 1 is obtained.

When, instead of 2,4-di-tert.butylphenol, phenol, p-cresol, m-tert.butylphenol, p-tert.butylphenol, 3,5-di-methylphenol, 2,4-di-tert.butyl-5-methylphenol, 2,4-di-tert.amylphenol, 2,4-di-methylphenol, 3-(4-hydroxyphenyl)-propionicacidoctadecylester, 2,5-di-tert.butylphenol, m-cresol, 4-phenylphenol, 2-phenylphenol, resorcinolmonomethylether, resorcinol, stearicacid-3-hydroxyphenylester, 4-hydroxybenzoicacidmethylester, 2-tert.butylphenol, o-cresol, 2,4-di-hydroxybenzophenone, 2,4-dihydroxybenzoic acid, β-naphthol, resorcinol and 2,4-di-hydroxybenzoic acid are used and 1 or 2 equivalents of mandelic acid are reacted therewith; Compounds Nos. 1 to 3, 5 to 20 and 22 to 26 are obtained. Compounds Nos. 54 to 61 may be prepared in analogous manner. Compound No. 17 of Table 1 is obtained by esterifying Compound No. 16 with stearicacidchloride; Compound No. 21 by esterifying Compound No. 20 with stearylalcohol in accordance with known methods.

EXAMPLE 2

1.34 Parts of the Compound No. 1 of Table 1, 1.0 part cyclohexanone, 0.02 parts piperidinebenzoate and 20 parts toluene are mixed together and heated for 21 hours under reflux. The mixture is concentrated in a rotation evaporator. Then the residue is dissolved in 120 parts ether, the ether solution washed with water, dehydrated over Glauber's salts and evaporated to dryness. After recrystallization from methanol, white crystals, melting point 74°-75°, of Compound No. 27 of Table 1 are obtained.

Compounds Nos. 28 of Table 1, and 32 and 39 of Table 2 are prepared in analogous manner.

EXAMPLE 3

A solution of 10.14 parts diphenylamine in 40 parts ether is added dropwise to a solution of 5.67 parts α-chlorophenylacetylchloride in 8 parts ether, subsequently 2.92 parts triethylamine are added thereto. The mixture is heated to 40° for 15 hours, the residue is filtered-off and washed with water and ether. White crystals having a melting point of 143°-144° are obtained. 4.82 Parts of the crystalline product are added to 60 parts nitrobenzene and 4 parts aluminium chloride are added slowly portionwise thereto, whereupon the temperature rises to 30° and a clear yellow solution is obtained. After 3 hours the solvent is removed by evaporation and the residue is added to a mixture of 100 parts ice water and 80 parts conc. hydrochloric acid. The product is extracted with ether, then the combined ether solutions are washed with water, dehydrated with MgSO₄ and the ether is evaporated. The yellow oil is made crystalline by washing with petroleum ether (m.pt. 96°-98°). The product has the formula of Compound No. 30 of Table 1. Compounds 29 and 31 are made in analogous manner.

EXAMPLE 4

78.9 Parts of the compound of formula ##STR12## are dissolved in 450 parts diethyleneglycolmonomethylether. 39 Parts potassium cyanide and 6 parts potassium iodide are added thereto. At a temperature of 80°, 63 parts of water are added dropwise. The temperature is raised to 130° and the mixture is stirred for 16 hours at this temperature. After cooling to room temperature, 1000 parts ice water are added. After carefully acidifying with hydrochloric acid, a precipitate is formed which is dissolved in 400 parts ether. The organic phase is separated, washed with water, dehydrated over MgSO₄ and evaporated. The residue is added to toluene, heated to the boil for approximately 1 hour whereupon water of condensation separates out. After evaporating the solvent and recrystallizing from methanol a colourless crystalline product, melting point 88°-89°, which is of the formula No. 41 in Table 2, is obtained.

EXAMPLE 5

Using a compound of formula ##STR13## and proceeding in analogous manner to Example 4 Compound No. 42 of Table 2, is obtained.

                                      TABLE 1                                      __________________________________________________________________________      ##STR14##                                                                                                         m.pt.                                      No.                                                                               R.sub.2                                                                              R.sub.3  R.sub.4  R.sub.5  °C.                                 __________________________________________________________________________     1  H     H        H        H        113-115                                    2  H     CH.sub.3 H        H        103-104                                    3  H     H        C(CH.sub.3).sub.3                                                                       H        129-130                                    4  H     C(CH.sub.3).sub.3                                                                       H        C(CH.sub.3).sub.3                                                                       113-114                                    5  H     C(CH.sub.3).sub.3                                                                       H        H        133-134                                    6  CH.sub.3                                                                             H        CH.sub.3 H        99,5-100                                   7  CH.sub.3                                                                             C(CH.sub.3).sub.3                                                                       H        C(CH.sub.3).sub.3                                                                       147-149                                    8  H     C(CH.sub.3).sub.2 (C.sub.2 H.sub.5)                                                     H        C(CH.sub.3).sub.2 (C.sub.2 H.sub.5)                                                     oil                                        9  H     CH.sub.3 H        CH.sub.3 oil                                        10 H                                                                                     ##STR15##                                                                              H        H        35                                         11 C(CH.sub.3).sub.3                                                                    H        H        C(CH.sub.3).sub.3                                                                       126-129                                    12 H     H        CH.sub.3 H         66-109                                    13 H                                                                                     ##STR16##                                                                              H        H        104-106                                    14 H     H        H                                                                                        ##STR17##                                                                              112-124                                    15 H     H        CH.sub.3 O                                                                              H        126-128                                    16 H     H        OH       H        oil                                        17 H     H                                                                                        ##STR18##                                                                              H        68-70                                      18 H     COOCH.sub.3                                                                             H        H        oil                                        19 H     H        H        C(CH.sub.3).sub.3                                                                       129-130                                    20 H                                                                                     ##STR19##                                                                              H        CH.sub.3 oil                                        21 H                                                                                     ##STR20##                                                                              H        CH.sub.3 wax                                        22 H                                                                                     ##STR21##                                                                              OH       H        143-145                                    23 H     COOH     OH       H        oil                                        No. 24                                                                              ##STR22##                   m.pt. 181-183°                         No. 25                                                                              ##STR23##                   oil                                           No. 26                                                                              ##STR24##                   m.pt. 64-65°                           No. 27                                                                              ##STR25##                   m.pt. 74-75°                           No. 28                                                                              ##STR26##                   m.pt. 76-78°                           No. 29                                                                              ##STR27##                   m.pt. 114-116°                         No. 30                                                                              ##STR28##                   m.pt. 96-98°                           No. 31                                                                              ##STR29##                   m.pt. 182-185°                         __________________________________________________________________________

                                      TABLE 2                                      __________________________________________________________________________      ##STR30##                                                                     No.                                                                               R.sub.1    R R.sub.3      R.sub.5     m.pt. °C.                      __________________________________________________________________________     32                                                                                 ##STR31## --                                                                               C(CH.sub.3).sub.3                                                                           C(CH.sub.3).sub.3                                                                          90-95                                 33                                                                                 ##STR32## H C(CH.sub.3).sub.2CH.sub.2 C(CH.sub.3).sub.3                                                 C(CH.sub.3).sub.2 CH.sub.2 C(CH.sub.3).sub.3      34                                                                                 ##STR33## H C.sub.9 H.sub.19                                                                            H           oil                                   35                                                                                 ##STR34## H CH.sub.3     H           203-205                               36                                                                                 ##STR35## H CH.sub.3     CH.sub.3    175                                   37                                                                                 ##STR36## H H                                                                                            ##STR37##  116-118                               38                                                                                 ##STR38## H CH.sub.2 COOC.sub.18 H.sub.37                                                               C(CH.sub.3).sub.3                                                                          oil                                   39 CH(CH.sub.2).sub.10CH.sub.3                                                               H C(CH.sub.3).sub.3                                                                           C(CH.sub.3).sub.3                                                                          oil                                   40                                                                                 ##STR39## H CH.sub.3     H           65-66                                 41 H          H C(CH.sub.3).sub.3                                                                           C(CH.sub.3).sub.3                                                                          88-89                                 42 H          H CH.sub.2COOH C(CH.sub.3).sub.3                                                                          175-177                               43 H          H CH.sub.2COOC.sub.18 H.sub.37                                                                C(CH.sub.3).sub.3                                                                          50-53                                 44                                                                                 ##STR40## H                                                                                 ##STR41##   C(CH.sub.3).sub.3                                                                          oil                                   45                                                                                 ##STR42## H CH.sub.2SC.sub.12 H.sub.25                                                                  C(CH.sub.3).sub.3                                                                          oil                                   46                                                                                 ##STR43## H H            H           74-75                                 47  (CH.sub.2).sub.11CH.sub.3                                                                H C(CH.sub.3).sub.3                                                                           C(CH.sub.3).sub.3                                                                          oil                                   48                                                                                 ##STR44## H C(CH.sub.3).sub.3                                                                           C(CH.sub.3).sub.3                                                                          oil                                   49                                                                                 ##STR45## H C(CH.sub.3).sub.3                                                                            ##STR46##  wax                                   50                                                                                 ##STR47## --                                                                               C(CH.sub.3).sub.3                                                                           C(CH.sub.3).sub.3                                                                          70-72                                 51 CHCH(C.sub.6 H.sub.5).sub.2                                                               --                                                                               C(CH.sub.3).sub.3                                                                           C(CH.sub.3).sub.3                                                                          67-73                                 52                                                                                 ##STR48## H C(CH.sub.3).sub.3                                                                           C(CH.sub.3).sub.3                                                                          94-97                                 53                                                                                 ##STR49## H C(CH.sub.3).sub.3                                                                           C(CH.sub.3).sub.3                                                                          121-123,5                             __________________________________________________________________________     No. 54                                                                                  ##STR50##           glassy mass                                       No. 55                                                                                  ##STR51##           m.pt. 125-129° C.                          No. 56                                                                                  ##STR52##           oil                                               No. 57                                                                                  ##STR53##           oil                                               No. 58 & No. 59                                                                         ##STR54##           58. R = H m.pt. 175-177° 59. R =                                        C.sub.18 H.sub.35 m.pt. 50-53°             No. 60                                                                                  ##STR55##           m.pt. 52-58°                               No. 61                                                                                  ##STR56##           m.pt. 123-132°                             __________________________________________________________________________

EXAMPLE A

A mixture of 1200 parts of a commercially available unstabilized polypropylene (Profax 6501), 0.6 parts calciumstearate, 0.6 parts tetrakis-[methylene-3(3',5'-di-tert.-butyl-4'-hydroxyphenyl)-propionate]-methane and 0.6 parts of the Compound No. 4 of Table 1 are shaken together for 10 minutes and extruded at 120 revs/min with temperatures of 150°, 240°, 260°, and 200° in the different heating areas of the extruder to form a strand which is granulated after passing through a water bath. The granulate is extruded and granulated a further 9 times, each time a part is taken to measure the Melt Flow Index (MFI according to ASTM D 1238 L, 230°; 2.16 kg) which serves as a measure of the thermomechanical oxidative degradation of a polymer. A control without Compound 4 of the Table is also extruded in like manner and tested. In comparison, the polymer containing Compound No. 4 of the Table exhibits a greatly improved melt stability during continuous extrusion. The other compounds of the Table may be employed in like manner.

EXAMPLE B

100 Parts unstabilized HD-polyethylene powder (Phillips Type) are stabilized with 0.02 parts Compound No. 5 of Table 1 and 0.01 parts tetrakis-[methylene-3(3',5'-di-tert.-butyl-4'-hydroxyphenyl)-propionate]-methane. The powder is subjected to a modified MFI Test at 230°/0.325 kg on a Davenport-MFI apparatus. The powder is pushed into a heated steel cylinder and a 325 g weight is placed thereon. The polymer which is pressed out is cut off at 60 second intervals. The amount is calculated in terms of g/10 min. The stronger the crosslinking of the polymer owing to insufficient stabilization, the lower the MFI value. After 5 to 15 minutes a constant value is obtained. The other compounds of the Tables may be used in analogous manner.

EXAMPLE C

1.0 Part octylstearate, 1.5 parts Ba-Cd stabilizer (powder), 1 part of Compound No. 4 of Table 1 and 0.5 parts of a commercially available arylalkylphosphate are mixed with 100 parts commercially available dispersion PVC (k-value-60) in a Fluid Mixer (Papenmeier Type TEHK8) until the temperature has risen to 110°. The homogeneous mixture is rolled on rollers heated to 180° for 1 minute and then pressed into plates (thickness 1 mm) at 200° for 1.5 min. at 2 atm. and 1.5 minutes at 20 atm. The test or plates are put into an air circulating drying cabinet at 180° for 30 minutes. A comparison sample which contained 2.5 parts Ba-Cd stabilizer instead of Compound No. 4 and 1.5 parts of the Ba-Cd stabilizer was also treated in the same manner. This sample undergoes discolouration even at the beginning of the heat treatment and is markedly more discoloured after the 30 minutes than the sample containing Compound No. 4 of Table 1.

EXAMPLE D

300 Parts ABS powder (Fa. Marbon AOE 30/075) are dissolved in 2200 parts chloroform and the solution is dropped into 8000 parts methanol whereupon the ABS is precipitated. After filtration the polymer which is now free from stabilizer is treated in vacuo overnight to remove all the solvent. 100 parts of the so-treated ABS powder is dissolved in chloroform and 0.2 parts Compound No. 10 of Table 1 are added thereto and the whole is stirred under nitrogen atmosphere for 15 minutes. The solution is drawn into a film with a 1 mm doctor blade onto a glass plate and is left for the solvent to evaporate-off whereby the film shrinks to 150μ thickness, and is freed from the rest of the solvent overnight at room temperature in vacuo. The film is then stoved in an air-circulating oven at 95°. By repeated IR-measurement to Δε=0.4 at 1715 cm⁻¹ the ageing resistance is checked. The samples containing the benzofuranone compound have longer resistance than the control samples which contain no stabilizer.

EXAMPLE E

100 Parts granulated polyethyleneterephthalate are ground to a rough powder and dried overnight at 100° in a vacuum drying cabinet. 1.0 Part of Compound No. 38 of Table 2 is added and the mixture is homogenised, then granulated in an extruder, spun into fibres at 280°, stretched (120 den/14) and twisted. The fibres are wound on to white cards and exposed to the light in an Atlas Weatherometer for 24 hour intervals. In comparison to a non-stabilized control, the sample containing Compound No. 41 has less tendency to yellow during the exposure to light and can be left in the Weatherometer for a substantially longer period of time in order to reach the same decrease in the tensile strength (50%).

EXAMPLE F

49.5 Parts Compound No. 4 of Table 1, 49.5 parts tetrakis-[methylene-3-(3',5'-di-tert.-butyl-4'-hydroxyphenyl)-propionate]-methane, 1 part calcium stearate and 0.02 parts (7-[2H-naphthol(1,2d)triazol-2-yl]-3-phenylcumarine (optical brightener) are heated to 160°. The mixture melts with stirring and the melt is poured into a flat dish and ground after cooling. The product obtained melts at 70°-75°.

0.5 Parts of the ground melt are mixed in a plastic bag by repeated shaking with 1000 parts unstabilized HDPE powder (Ziegler Type, MFI 190/z=0.7). 43 Parts of the powder mixture are heated to 220° in a Brabender Plasti-Corder PLV 151 extruder at 50 revs/min. until there is a sharp drop in the torque indicating polymer degradation. In comparison to a sample stabilized with double the amount of a 1:1 mixture of tetrakis-[methylene-3-(3',5'-di-tert.-butyl-4'-hydroxyphenyl)-propionate]-methane, and 2,6-di-tert.-butyl-4-methylphenol the test sample exhibits superior stability.

When different concentrations of the above melt product are mixed with polyethylene or polypropylene powder and extruded into a strand which are subsequently ground, the fluorescence intensity can be measured to assess the concentration of additives in the polymer. 

What is claimed is:
 1. A process for stabilizing organic polymeric materials comprising incorporating therein a stabilizing amount of a compound of formula Ic, ##STR57## in which either R is hydrogen, andR₁ hydrogen; C₁₋₂₂ alkyl; C₅ or C₆ cycloalkyl; C₁₋₅ alkyl-C₅ or C₆ cycloalkyl; phenyl; phenyl substituted by one to three substituents selected from the group consisting of C₁₋₁₂ --alkyl, hydroxy, C₁₋₁₂ alkoxy, C₁₋₁₈ --acyloxy, chloro or nitro, with the provisos that: (1) when the phenyl ring contains more than one C₁₋₁₂ alkyl group, said alkyl groups contain a maximum of 18 carbon atoms, (2) the maximum number of hydroxy substituents is two, and (3) the maximum number of each of the substituents selected from C₁₋₁₂ alkoxy, C₁₋₁₈ acyloxy, chloro and nitro is one; or a group of formula (a/4), (a/5) or (a/6) ##STR58## or R and R₁ together form a group (a/2) ##STR59## either each of R₂ to R₅, independently, is hydrogen; C₁₋₁₂ alkyl; C₅ or C₆ cycloalkyl; C₁₋₅ alkyl-C₅ or C₆ cycloalkyl; C₁₋₂₂ alkoxy; phenoxy; phenoxy substituted by one or two C₁₋₁₂ alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; C₁₋₁₈ acyloxy; chloro; phenyl-C₁₋₉ alkyl; phenylthio; phenyl-C₁₋₉ alkyl or phenylthio substituted on the phenyl ring by one to three substituents selected from C₁₋₁₂ alkyl, hydroxy and R₁₅ CO--O--; phenyl; phenyl substituted by one or two C₁₋₁₂ alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; nitro; 2-furanylcarbonyloxy; 2-thienylcarbonyloxy; a group of formula (b/2), (b/3) or (b/4) ##STR60## a group of formula (a/4) or (a/5) as defined above; with the provisos that: (a) a maximum of two of R₂ through R₅ is C₅ or C₆ cycloalkyl, C₁₋₅ alkyl-C₅ or C₆ cycloalkyl, C₁₋₂₂ alkoxy, phenoxy, substituted phenoxy, C₁₋₁₈ acyloxy or chloro; and (b) a maximum of one of R₂ through R₅ is optionally substituted phenyl, phenyl-C₁₋₉ alkyl or phenylthio, nitro, 2-furanylcarbonyloxy, 2-thienylcarbonyloxy or a group of formula (b/2), (b/3), (b/4), (a/4) or (a/5), provided that only the R₃ substituent can be a group of formula (b/3) or (b/4) and only the R₃ or R₅ substituent can be a group of formula (a/5); or R₂ and R₃, together, form a condensed benzene ring, or R₃ and R₄, together, form a furan(2) one ring in which the 3-position bears the substituents R and R₁ as defined above, or R₄ and R₅, together, form tetramethylene or a furan(2) one ring in which the 3-position bears the substituents R and R₁ as defined above, and one of the two remaining substituents is hydrogen and the other is any one of the significances given for R₂ to R₅ above;either R₆ is C₁₋₁₈ alkyl; C₅ or C₆ cycloalkyl; C₁₋₅ alkyl-C₅ or C₆ cycloalkyl; benzyl; (C₆ H₅)₂ CH; phenyl; phenyl mono- or disubstituted by C₁₋₁₂ alkyl, provided that when the phenyl ring contains more than one C₁₋₁₂ alkyl group, said alkyl groups contain a maximum of 16 carbon atoms; phenyl monosubstituted by hydroxy; phenyl mono- or disubstituted by methoxy; phenyl monosubstituted by chloro; phenyl monosubstituted by dimethylamino; 3,5-di-tertiary butyl-4-hydroxyphenyl; β-naphthyl; pyridinyl; 2-furyl; or a group of formula (c/1) or (c/2) ##STR61## R_(6a) is hydrogen; C₁₋₁₈ alkyl; C₅ or C₆ cycloalkyl; C₁₋₅ alkyl-C₅ or C₆ cycloalkyl; phenyl or benzyl;or R₆ and R_(6a), together with the carbon atom to which they are bound, form an unsubstituted 5- or 6-membered aliphatic ring or a 5- or 6-membered aliphatic ring monosubstituted by C₁₋₄ alkyl;each R₇, independently, is hydrogen; C₁₋₁₈ alkyl; alkyl-O-alkylene having a maximum of 18 carbon atoms; alkyl-S-alkylene having a maximum of 18 carbon atoms; di-C₁₋₄ alkylamino-C₁₋₈ alkyl; C₅₋₇ cycloalkyl; phenyl; or phenyl substituted by one to three C₁₋₁₂ alkyl groups, said alkyl groups having a maximum of 18 carbon atoms;either each R₈, independently, is hydrogen; C₁₋₁₈ alkyl; C₅ or C₆ cycloalkyl; C₁₋₅ alkyl-C₅ or C₆ cycloalkyl; phenyl; phenyl substituted by one or two C₁₋₁₂ alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; or a group of formula (d/1), (d/2) or (d/3) ##STR62## or both R₈ 's, together with the nitrogen atom, form an unsubstituted piperidine or morpholine ring; R₉ has one of the significances of R₈ ; R_(9a) is hydrogen; C₁₋₁₈ alkyl; or a group of formula (d/1), (d/2) or (d/3) as defined above; R₁₁ is hydrogen; C₁₋₂₂ alkyl; C₅₋₇ cycloalkyl; phenyl; phenyl-C₁₋₆ alkyl; or phenyl or phenyl-C₁₋₆ alkyl substituted on the phenyl ring by one or two C₁₋₁₂ -alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; R₁₂ is C₁₋₁₈ alkyl; 2-hydroxyethyl; phenyl; or C₁₋₉ alkylphenyl; R₁₅ is C₁₋₂₂ alkyl or phenyl; and n is 0, 1 or
 2. 2. A process according to claim 1, in which either R₆ is C₁₋₁₈ alkyl, phenyl, 3,5-di-tertiary butyl-4-hydroxyphenyl or a group of formula (c/1), and R_(6a) is hydrogen or C₁₋₁₂ alkyl, or R₆ and R_(6a), together with the carbon atom to which they are bound, form a cyclohexylidene ring; each R₇, independently, is hydrogen, C₁₋₁₈ alkyl, phenyl or phenyl substituted by one or two C₁₋₁₂ alkyl groups, said alkyl groups having a maximum of 16 carbon atoms; either each R₈, independently, is hydrogen or C₁₋₁₈ alkyl, or both R₈ 's, together with the nitrogen atom, form an unsubstituted piperidine ring; R₉ and R_(9a), independently, are hydrogen, C₁₋₈ alkyl or a group of formula (d/1); R₁₂ is C₁₋₁₂ alkyl, phenyl or C₁₋₉ alkylphenyl, wherein the alkyl group is in the 4-position of the phenyl ring; and n in (a/4) or (a/5) as R₁ or R₅ is 1, and n in (a/4) or (a/5) as R₃ is
 2. 3. A process according to claim 2, in which either R is hydrogen and R₁ is hydrogen, C₁₋₁₈ alkyl, phenyl, phenyl substituted by one to three substituents selected from C₁₋₈ alkyl and hydroxy, with the proviso that the maximum number of C₁₋₈ alkyl substituents is two and the maximum number of hydroxy substituents is one, or a group of formula (a/4) or (a/5), or R and R₁, together, form a group of formula (a/2), where R₆, R_(6a), R₇, R₈ and n are as defined in claim 2; R₂ is hydrogen or C₁₋₄ alkyl; R₃ is hydrogen, C₁₋₁₂ alkyl, phenyl, C₁₋₁₈ alkoxy, phenoxy, C₁₋₁₈ alkylcarbonyloxy, a group of formula (a/4), (a/5), (b/2) or (b/4), where R₇, R₈ and n are as defined above or, together with R₂, forms a condensed benzene ring; R₄ is hydrogen, C₁₋₁₂ alkyl, C₁₋₁₈ alkoxy, phenoxy or, together with R₃, forms a furan(2)one ring in which the 3-position bears the substituents R and R₁, where R is hydrogen and R₁ is as defined above; and R₅ is hydrogen, C₁₋₁₂ -alkyl, phenyl, a group of formula (a/4) or (a/5), where R₇, R₈ and n are as defined above, a group of formula (PA) or (PT) ##STR63## in which each R_(x), independently, is hydrogen or C₁₋₄ alkyl,R_(y) is hydrogen or a group --CO--R₁₅, where R₁₅ is C₁₋₂₂ alkyl or phenyl, each R_(z), independently, is hydrogen or C₁₋₉ alkyl, and R_(z) ' is hydrogen or C₁₋₄ linear alkyl, with the proviso that at least one R_(z) or R_(z) ' must be hydrogen, or, together with R₄, forms tetramethylene or a furan(2)one ring.
 4. A process according to claim 3, in which when R₂ and R₃, together, form a condensed benzene ring or R₃ and R₄, together, form a furan(2)one ring or R₄ and R₅, together form a furan(2)one ring or tetramethylene, one of the two remaining substituents R₂ to R₅ is hydrogen and the other is hydrogen, COOH or C₁₋₄ alkyl, with the proviso that R₃ and R₅ cannot be carboxy.
 5. A process according to claim 4, in which R₁ is C₁₋₁₈ alkyl, phenyl or phenyl substituted by one to three substituents selected from C₁₋₈ alkyl and hydroxy, with the proviso that the maximum number of C₁₋₈ alkyl substituents is two and the maximum number of hydroxy substituents is one.
 6. A process according to claim 5, in which R₁ is phenyl or phenyl monosubstituted by C₁₋₄ alkyl.
 7. A process according to claim 1, in which R₁ is p-methoxyphenyl; R, R₂ and R₄ are hydrogen, and R₃ and R₅ are tert.-butyl.
 8. A process according to claim 1, in which, in the compound of formula I_(c), where any one of R₂ to R₅ form a benzene ring or furan(2)one ring or tetramethylene one of the remaining substituents R₂ to R₅ is hydrogen and the other is hydrogen, COOH or C₁₋₄ alkyl.
 9. A process according to claim 1 in which any optionally substituted phenylalkyl or phenylthio as R₂ to R₅ is in the 5- or 7-position.
 10. A process according to claim 9, in which when R₃ is optionally substituted phenylalkyl or phenylthio, R₂ and R₄ are hydrogen and R₅ is hydrogen or C₁₋₅ alkyl and when R₅ is optionally substituted phenylalkyl or phenylthio R₂ and R₄ are hydrogen and R₃ is hydrogen or C₁₋₈ alkyl.
 11. A process according to claim 9, in which any optionally substituted phenylalkyl or phenylthio is in the 7-position.
 12. A process according to claim 3, in which when R₅ is (PA) or (PT), R₂ and R₄ are both hydrogen and R₃ is hydrogen or C₁₋₈ alkyl.
 13. A process according to claim 1, in which the polymeric material is polypropylene, polyethylene, ethylene/propylene copolymers, polybutylene, polystyrene, PVC, polyesters, polyamides, polyurethanes, polyacrylonitrile, ABS terpolymers, terpolymers of acrylic ester, styrene and acrylonitrile, copolymers of styrene and acrylonitrile and styrene/butadiene copolymers.
 14. A process according to claim 1, in which the polymeric material is polypropylene.
 15. A process according to claim 1, in which the polymeric material is polyethylene or an ethylene/propylene. copolymer.
 16. A process according to claim 15, in which the polymeric material is high density (HD) polyethylene.
 17. A process according to claim 1, in which from 0.01 to 5%, based on the weight of the polymeric material, of a compound of formula Ic is incorporated in the polymeric material to be stabilized.
 18. A process according to claim 1, in which a compound of formula Ic is incorporated into the polymeric material by melt blending.
 19. Polymeric organic material stabilised with a compound of formula Ic, as defined in claim
 1. 20. A process according to claim 1, in which R₁ is phenyl and R is hydrogen.
 21. A process according to claim 1, in which R₁ is phenyl, R, R₂ and R₄ are hydrogen and R₃ and R₅ are C₁₋₅ alkyl.
 22. A process according to claim 21, in which R₃ and R₅ are methyl, tert.-butyl or tert.-amyl or R₃ is methyl and R₅ is tert.-butyl.
 23. A process according to claim 1 comprising incorporating a compound of formula I_(c) together with either (i) a stabilizer of the sterically hindered phenol type or (ii) a stabilizer of the thiodipropionate, thiopropionate, dialkylsulphide, aryl phosphite, aryl diphosphonite and tetraoxadiposphaspiroundecane type, or (i) and (ii), into the polymeric material to be stabilized.
 24. A process according to claim 1, in which R₁ is phenyl; R, R₂ and R₄ are hydrogen, and R₃ and R₅ are tert.-butyl. 